In related art, an imaging device, such as a digital camera and a digital video camera, which records a shot image using an image sensor has been developed. The image sensor has a pixel unit and a peripheral circuit unit. The peripheral circuit unit reads out a signal from a pixel and outputs the signal as an image signal. The pixel unit performs photoelectric conversion using a photodiode, and a signal obtained through photoelectric conversion is read out to the peripheral circuit unit through a pixel circuit formed in the pixel unit.
In recent years, while it is desired to make such an imaging device have more pixels, higher image quality and higher speed, it is also desired to make the imaging device further smaller. As an imaging device which satisfies such desires, a laminate type imaging device is proposed. The laminate type imaging device has a structure in which a chip on which a signal processing circuit is formed is used in place of a support substrate of the imaging device, and a pixel portion is superimposed thereon. It is proposed to make the imaging device smaller by employing such a structure (see, for example, Patent Literature 1 to Patent Literature 3).